we have had it for about a year now, the van runs good, but we smell gas once and a while when we get out or when its been idling for a while. O2 sensor?

and every once and a while the van shuts of without warning nice a smooth smoother than with the key, any ideas?

i am planning to replae the O2 sensors as soon as i get them

1996 e-150 jayco conversion
351w 140,000 miles

would also like shock recomendations